1. Field of the Invention
The present invention relates to a data transmission apparatus and a method for transmitting data, and in particular, to a data transmission apparatus for transmitting digital video and audio data between respective audio visual apparatuses, such as a digital video cassette recorder (referred to as a digital VCR) or the like, and a method therefor.
2. Description of the Related Art
There has been currently under development of digital VCRs for recording video and audio in a form of digital signals expressed by 0s and 1s, respectively, for the purpose of achieving high-quality video and audio. One of major features of the digital VCRs is that the qualities of video and audio signals are not deteriorated through dubbing these signals. In the digital VCR, an audio signal, a video signal and the other control signal or the like are recorded in a form of digital signals on a magnetic tape, respectively.
Since transmission of data is executed in a form of a digital signal between the digital VCRs, the transmitted data does not change in the transmission stage. Therefore, the recorded data can be transmitted as it is from an audio visual apparatus to another audio visual apparatus.
In particular, in a digital VCR for consumer use, the video signal is recorded onto the magnetic tape in a form of a compressed video signal so that the amount of data to be recorded thereonto can be reduced for the purpose of reducing the amount of consumption of the magnetic tape. In order to transmit a video signal reproduced by a digital VCR therefrom to another digital VCR in a form of an analog signal and to record the transmitted video signal in the latter VCR, the reproduced video signal is decompressed so as to be converted into an analog video signal. The analog video signal is inputted to the digital VCR in which the video signal is to be recorded. In the digital VCR, the analog video signal is converted into a digital video signal so as to be compressed again. Through the above-mentioned compression and decompression processes, the quality of the image of the video signal may deteriorate.
In the case when transmitting the video signal in a form of a compressed digital signal, there is a great advantageous effect of causing no deterioration of the quality of the image thereof due to the transmission process because the compression and decompression processes are not required.
For the digital VCR is defined a digital interface for transmitting video and audio signals in a form of digital signals. In the digital VCR, one track is segmented into a plurality of sectors, and then a subcode for the video and audio signals, time code, and the like are recorded in respective sectors. In a general digital interface, data to be recorded in the sectors are transmitted in a predetermined order.
The first problem to be solved by the present invention is as follows. When one field is a transmission unit, the period of one field is greatly different between the television broadcasting system having a frame frequency of 25 Hz such as SECAM system, PAL system or the like and another television broadcasting system having a frame frequency of 30 Hz such as NTSC system. Therefore, a time interval required for transmitting one transmission unit is greatly different depending on the television broadcasting system.
When transmitting data of a plurality of television broadcasting systems by means of an identical transmission medium between a plurality of audio visual apparatuses such as digital VCRs or the like, there is such a problem that the time interval for transmitting one transmission data unit is required to cope with a plurality of types of the transmission time.
The second problem to be solved by the present invention is as follows. In the case of implementing a digital VCR for consumer use, it may be required to transmit video and audio signals of both of the high-definition television (HDTV) broadcasting system such as High-Vision system or the like and the current television broadcasting system such as NTSC system or the like between a plurality of digital VCRs or the like. In order to achieve cost reduction, it is required to provide an identical transmission path line in both of the case where the signals of the current television broadcasting system are transmitted and the case where the signals of the high-definition television broadcasting system are transmitted. However, the amount of information of the video signal of the high-definition television broadcasting system is much greater than that of the current television broadcasting system. Since the amount of data is greatly different between the signals of the high-definition television broadcasting system and the signals of the current television broadcasting system, there is such a problem that data of the signals of the current television broadcasting system and the data of the signals of the high-definition television broadcasting system are compelled to be transmitted in different manners.
The third problem to be solved by the present invention is as follows. Since any conventional digital VTR copes with only the standard television signal such as an NTSC television signal, a SECAM television signal, a PAL television signal or the like, then the other type of inputted signal cannot be recorded in the conventional digital VTR. On the other hand, in order to increase the number of types of signals which can be inputted and recorded onto a magnetic tape, there has been suggested a method of changing either the number of sectors or the structure of sectors in each track. In this case, not only a track structure flag representing the number, arrangement and the like of sectors in a track, but also a sector structure flag representing, for each sector represented by the track structure flag, the structure of the sector are to be recorded within the track on the magnetic tape.
However, the conventional digital interface has such a problem that it cannot cope with the change of such track structure as described above since it communicates with other apparatuses always in a previously fixed format. Furthermore, since all the data including the other sectors are required to be transmitted even in the case where the data of a specified sector is desired to be transmitted, there is such a problem that the excessive transmission band for unnecessary transmission must be provided.
The fourth problem to be solved by the present invention is as follows. In the digital VCR, other than the video and audio signals, not only VAUX (Video Auxiliary) data representing the type, kind or the like of the television broadcasting system of the video signal, but also AAUX (Audio Auxiliary) data representing the sampling frequency or the like of the audio signal are additionally recorded onto the magnetic tape. The above-mentioned these information data are very important data necessary in reproducing the recorded video and audio signals in the reproduction stage. Therefore, the information data are repetitively recorded a plural of times in one frame period of the video signal. In transmitting the video and audio signals from the digital VCR to another digital VCR, the VAUX and AAUX data corresponding to the video and audio signals must be additionally transmitted thereto. In general, the data are transmitted a plurality of times in one frame period in conformity with the recorded tracks.
However, in a bad reproducing condition, the probability of occurrence of the phenomenon becomes higher that an error correcting process is executed by an error correcting function, wherein the phenomenon is referred to as an xe2x80x9cerror correctionxe2x80x9d hereinafter). Since the error-corrected data does not allow its error to be detected any more, then the error data is transmitted as it is. When there is no error or when an error has occurred and then appropriately corrected, the identical VAUX and AAUX data are transmitted a plurality of times in one frame period, and therefore, the proper process is required to be executed in response to the received data on the receiver side.
However, when the error correction is performed, there is such a possibility that different VAUX and AAUX data or the like are transmitted in one frame period. In such a case, it is impossible to discriminate which VAUX and AAUX data are correct on the receiver side, and then this results in such a problem that the television broadcasting system can not be correctly selected, and the sampling frequency can not be correctly set.
In order to solve the above-mentioned problems, an essential object of the present invention is to provide a data transmission apparatus and a method capable of transmitting digital video and audio data of a plurality of television broadcasting systems, between a plurality of audio visual apparatuses such as digital VCRs.
Another object of the present invention is to provide a data transmission apparatus and a method capable of transmitting digital video and audio data of both of the high-definition television broadcasting system and the current television broadcasting system, between a plurality of audio visual apparatuses such as digital VCRs.
A further object of the present invention is to provide a data transmission apparatus and a method having a flexibility of data transmission, capable of transmitting a part or the whole part of various kinds of data with changing a data format thereof.
A still further object of the present invention is to provide a data transmission apparatus and a method capable of transmitting the identical additional data such as the VAUX data, the AAUX data or the like, together with digital video and audio data, by unifying the additional data in one frame
According to one aspect of the present invention, there is provided a data transmission apparatus comprising:
block forming means for forming a plurality of data blocks of transmission data composed of at least one of digital video data, digital audio data, and digital auxiliary data related to said digital video data and said digital audio data, and outputting said plurality of data blocks; and
grouping means for grouping said plurality of data blocks outputted from said block forming means so as to form transmission group data of one transmission unit block having a time length of approximately one three-hundredth second, and for transmitting said transmission group data.
Further, there is provided a method of transmitting data, including the steps of:
forming a plurality of data blocks of transmission data composed of at least one of digital video data, digital audio data, and digital auxiliary data related to said digital video data and said digital audio data, and outputting said plurality of data blocks;
grouping said plurality of data blocks so as to form transmission group data of one transmission unit block having a time length of approximately one three-hundredth second; and
transmitting said transmission group data.
The present invention has such an advantageous effect as enabling transmission of the digital video and audio data of all the television broadcasting systems having frame frequencies of 25 Hz and 30 Hz by dealing with transmission executed approximately every one three-hundredth second.
The above-mentioned data transmission apparatus preferably further comprises classifying means for classifying said transmission group data into a plurality of sections, by adding section identification data to each said transmission group data.
The above-mentioned method preferably further includes a step of classifying said transmission group data into a plurality of sections, by adding section identification data to each said transmission group data.
The present invention produces such an advantageous effect of enabling transmission of the video and audio data of, for example, the high-definition television broadcasting system in a manner similar to that in the current broadcasting system by transmitting the digital video and audio data through classification thereof into a plurality of sections in such a case as the high-definition television broadcasting system having a great number of data blocks to be transmitted.
According to another aspect of the present invention, a data transmission apparatus for transmitting inputted digital data to be recorded in a plurality of sectors of each track on a recording medium, together with inputted first application ID data representing a structure of each said track and inputted second application ID data representing a structure of each of said sectors, comprising:
DIF-ID generating means for generating digital interface ID data including said inputted second application ID data, in response to said inputted second application ID data;
at least one block forming means for forming a data block including said digital data to be recorded and said digital interface ID data generated by said DIF-ID generating means, and outputting said data block;
header DIF block generating means for generating header digital interface block data including said inputted first application ID data; and
grouping multiplexing means for time-multiplexing said header digital interface block data generated by said header DIF block generating means and said data block generated by said block forming means to form transmission digital data so that said data block follows said header digital interface block data, and transmitting said transmission digital data.
In the above-mentioned data transmission apparatus, said DIF-ID generating means preferably generates digital interface ID data including said inputted second application ID data and a transmission flag, in response to said inputted second application ID data and inputted transmission flag, said transmission flag representing whether or not data, to be recorded in a sector represented by said second application ID data which is in a track represented by said first application ID data within said header digital interface block data generated by said header DIF block generating means, is to be transmitted.
In the above-mentioned data transmission apparatus, said header DIF block generating means preferably generates header digital interface block data including application ID data representing that said first application ID data is indefinite, when said first application ID data is indefinite.
In the above-mentioned data transmission apparatus, said DIF-ID generating means preferably generates digital interface ID data including application ID data representing that said second application ID data is indefinite, when said second application ID data is indefinite.
The data transmission apparatus preferably further comprises:
memory means for storing said first and second application ID data;
wherein said DIF-ID generating means generates digital interface ID data including said second application ID data of the previous sector stored in said memory means, when there is no inputted second application ID data, and
wherein said header DIF block generating means generates header digital interface block data including said first application ID data of the previous track stored in said memory means, when there is no inputted first application ID data.
According to a further aspect of the present invention, there is provided a method for transmitting inputted digital data to be recorded in a plurality of sectors of each track on a recording medium, together with inputted first application ID data representing a structure of each said track and inputted second application ID data representing a structure of each of said sectors, including the steps of:
generating digital interface ID data including said inputted second application ID data, in response to said inputted second application ID data;
forming a data block including said digital data to be recorded and said digital interface ID data generated in said generating digital interface ID data step, and outputting said data block;
generating header digital interface block data including said inputted first application ID data; and
time-multiplexing said header digital interface block data generated in said generating header digital interface block data step and said data block generated in said forming step to form transmission digital data so that said data block follows said header digital interface block data, and transmitting said transmission digital data.
In the above-mentioned method, said generating digital interface ID data step preferably includes a step of generating digital interface ID data including said inputted second application ID data and a transmission flag, in response to said inputted second application ID data and inputted transmission flag, said transmission flag representing whether or not data, to be recorded in a sector represented by said second application ID data which is in a track represented by said first application ID data within said header digital interface block data generated in said generating header digital interface block data step, is to be transmitted.
In the above-mentioned method, said generating header digital interface block data step preferably includes a step of generating digital interface block data including application ID data representing that said first application ID data is indefinite, when said first application ID data is indefinite.
In the above-mentioned method, said generating digital interface ID data step preferably includes a step of generating digital interface ID data including application ID data representing that said second application ID data is indefinite, when said second application ID data is indefinite.
The above-mentioned method preferably further includes a step of:
storing said first and second application ID data in memory means;
wherein said generating digital interface ID data step includes a step of generating digital interface ID data including said second application ID data of the previous sector stored in said memory means, when there is no inputted second application ID data, and
wherein said generating header digital interface block data step includes a step of generating header digital interface block data including said first application ID data of the previous track stored in said memory means, when there is no inputted first application ID data.
With the above-mentioned arrangement, therefore, by receiving the header digital interface (DIF) block data, the structure such as a format of the data block subsequent to the header DIF block can be identified. Therefore, according to the present invention, for example, no matter how the recording format changes, the digital interface format can be changed into a format appropriate for the recording format.
According to a still further aspect of the present invention, there is provided a data transmission apparatus for transmitting inputted digital video data and digital audio data together with inputted digital auxiliary data related to said digital video data and said digital audio data, said digital auxiliary data being transmitted a plurality of times in one frame, comprising:
at least one data extracting means for extracting said inputted digital auxiliary data from input data including said digital video data, said digital audio data and said digital auxiliary data;
at least one majority means for counting the respective numbers of the digital auxiliary data having the same contents among a plurality of inputted digital auxiliary data, and selecting and outputting the auxiliary data of the greatest counted number in one frame;
delay means for delaying said input data including said digital video data, said digital audio data and said digital auxiliary data by a time interval of one frame, and outputting said input data; and
switching means for switching said input data outputted from said delay means and said auxiliary data of the greatest counted number in one frame outputted from said majority means, so as to output and transmit said digital video data, said digital audio data and said digital auxiliary data, together with said auxiliary data of the greatest counted number in one frame outputted from said majority means, by replacing said auxiliary data included in said input data, with said auxiliary data of the greatest counted number in one frame outputted from said majority means.
In the above-mentioned data transmission apparatus, said majority means preferably counts the respective numbers of the digital auxiliary data having the same contents related to said audio data, every channel of said audio data, among a plurality of inputted digital auxiliary data related to said audio data, and selects and outputs the auxiliary data of the greatest counted number in one frame which is related to said audio data.
According to a still more further aspect of the present invention, there is provided a method for transmitting inputted digital video data and digital audio data together with inputted digital auxiliary data related to said digital video data and said digital audio data, said digital auxiliary data being transmitted a plurality of times in one frame, including:
extracting said inputted digital auxiliary data from input data including said digital video data, said digital audio data and said digital auxiliary data;
counting the respective numbers of the digital auxiliary data having the same contents among a plurality of inputted digital auxiliary data, and selecting and outputting the auxiliary data of the greatest counted number in one frame;
delaying said input data including said digital video data, said digital audio data and said digital auxiliary data by a time interval of one frame, and outputting said input data; and
switching said delayed input data and said outputted auxiliary data of the greatest counted number in one frame, so as to output and transmit said digital video data, said digital audio data and said digital auxiliary data, together with said outputted auxiliary data of the greatest counted number in one frame, by replacing said auxiliary data included in said input data, with said outputted auxiliary data of the greatest counted number in one frame.
In the above-mentioned method, said counting step preferably includes a step of counting the respective numbers of the digital auxiliary data having the same contents related to said audio data, every channel of said audio data, among a plurality of inputted digital auxiliary data related to said audio data, and selecting and outputting the auxiliary data of the greatest counted number in one frame which is related to said audio data.
According to the present invention, in regard to important auxiliary data which have identical contents and recorded a plurality of times in one frame on a recording medium such as magnetic tape, when auxiliary data having different contents are reproduced within one frame due to reproduction error or the like, the auxiliary data are transmitted with their contents unified to the contents presumed to be most accurate. With the above-mentioned arrangement, the auxiliary data having identical contents can be obtained on the receiver side, for example, thereby allowing a digital VCR to be set based on the auxiliary data.